Actuator with plurality of torsion bars having varying spring constant

Abstract

An actuator (1) is provided with: a movable part (120); a support part (110, 210) which supports the movable part; and a plurality of torsion bars (230) (i) each of which connects the movable part and the support part along a long direction such that the movable part is capable of swinging around a rotational axis which is along the long direction and (ii) which are arranged along a short direction; the farther each torsion bar is from the rotational axis, the smaller a spring constant of each torsion bar is.

The invention claimed is: 
     
       1. An actuator comprising:
 a support part which supports a movable part; and 
 a plurality of torsion bars each of which connects the movable part and the support part such that the movable part is capable of swinging around a rotational axis which is along a long direction, wherein, 
 the plurality of torsion bars are arranged along a short direction of the torsion bars in a liner symmetric manner with respect to the rotational axis, 
 the farther each torsion bar is from the rotational axis, the smaller a spring constant of each torsion bar is, 
 at least one of the plurality of torsion bars includes a bending part and connecting parts, 
 the bending part includes: a first part, a second part, and a third part, each of the first part and the second part extends along the short direction, the third part extends along the long direction and connects the first and second parts, 
 one of the connecting parts connects the bending part and the movable part and the other one of the connecting parts connects the bending part and the support part, and 
 each of the connecting parts extends in parallel with the rotational axis. 
 
     
     
       2. The actuator according to  claim 1 , wherein the farther each torsion bar is from the rotational axis, the smaller a width of each torsion bar is. 
     
     
       3. The actuator according to  claim 1 , wherein the farther each torsion bar is from the rotational axis, the smaller a density of each torsion bar is. 
     
     
       4. The actuator according to  claim 3 , wherein one or more hole is formed in at least one of the plurality of torsion bars. 
     
     
       5. The actuator according to  claim 1 , wherein the farther each torsion bar is from the rotational axis, the larger a length of each torsion bar is. 
     
     
       6. The actuator according to  claim 5 , wherein at least one of the plurality of torsion bars has such a turning shape that the at least one of the plurality of torsion bars turns around at least once or more toward a direction which is opposite to a direction along which at least one of the plurality of torsion bars extends from the support part to the movable part. 
     
     
       7. The actuator according to  claim 6 , wherein
 at least one of the other torsion bars other than one or two torsion bar which is located on the rotational axis or is closest to the rotational axis among the plurality of torsion bars has the turning shape, and 
 one or two torsion bar which is closest to the rotational axis among the plurality of torsion bars does not have the turning shape. 
 
     
     
       8. The actuator according to  claim 1 , wherein,
 a central torsion bar that is one of the plurality of torsion bars and that is located on or that is closest to the rotational axis is disposed between a first torsion bar and a second torsion bar each of which is one of the plurality of torsion bars and that includes the bending part, and 
 the central torsion bar does not include the bending part and linearly extends from the support part to the movable part. 
 
     
     
       9. The actuator according to  claim 8 , wherein each of the first and second torsion bars includes the bending part in which the third part bends to be away from the central torsion bar along the short direction. 
     
     
       10. The actuator according to  claim 9 , wherein,
 the plurality of torsion bars includes: a third torsion bar that is adjacent to the first torsion bar along the short direction and that is farther from the rotational axis along the short direction than the first torsion bar is; and a fourth torsion bar that is adjacent to the second torsion bar along the short direction and that is farther from the rotational axis along the short direction than the second torsion bar is, 
 the third torsion bar includes the bending part in which the third part bends to be closer to the connecting part of the first torsion bar, and 
 the fourth torsion bar includes the bending part in which the third part bends to be closer to the connecting part of the second torsion bar.